Radio frequency ablation (RFA) has become a common treatment for treating specific cardiac arrhythmias. Portions of the heart sometimes form alternative conduction pathways which interfere with the normal conduction of the electrical signals which regulate the beating of the heart thereby causing some cardiac arrhythmias to occur. In order to remove these alternative conduction pathways, the heart is first mapped through catheter mapping procedures in order to find where these alternative conduction pathways are located, and then RFA is used to prevent these areas of the heart from disrupting the normal conduction patterns of the heart.
RFA typically involves the use of a specialized ablation catheter which is positioned at the site of the alternative conduction pathway. Radio frequency (RF) waves are then typically delivered through the ablation catheter and onto the alternative conduction pathway. The radio frequency waves create heat at the site of the alternative conduction pathway creating a lesion which destroys the tissues forming the alternative conduction pathways.
Ablation catheters have been developed in order to deliver radio frequency waves at the site of the abnormal pathway. While some of these prior art ablation catheters are well suited for particular procedures, the ability of these prior art ablation catheters to perform a variety of procedures effectively have been limited due to a number structural constraints which are necessitated by the spatial and physiological requirements of the applications in which these ablation catheters are to be used. Size, flexibility, and maneuverability are common restraints which have previously prevented more effective ablation catheter designs.
One drawback to the prior art is their inability to make a variety of lesions. There are typically two types of lesions which are generated by ablation catheters. One type of lesion is a focal lesion where the RF wave is concentrated at a point. Typically, the prior art is limited to making focal lesions. A tip electrode carried on the distal tip of an ablation catheter is preferably used for making focal lesions. However, there are a variety of procedures in which linear lesions are preferred, requiring that the RF energy be delivered along a line. There are prior art ablation catheters which are capable of creating linear lesions; however, these prior art ablation catheters are not particularly suited for making focal lesions. A linear electrode is preferably utilized for making linear lesions. Although tip electrodes can also be used utilized for making linear lesions, the use of tip electrodes to make linear lesions can be significantly more difficult and time consuming.
The maneuverability of the prior art ablation catheters also limit their effectiveness. The ablation catheters are typically utilized within the interior chambers of the heart. The precise placement of the electrodes onto the site to which the RF waves are to be delivered and the sufficiency of the contact between an electrode and the site significantly impacts the effectiveness of the treatment. Linear electrodes, and especially longer linear electrodes, tend to be stiffer, making it more difficult for them to maneuver and to conform to the generally arcuate shape of the interior walls of the heart.
Another problem common amongst the prior art ablation catheters is the formation of coagulum around the electrode during ablation. The heat generated by the RFA sometimes causes the electrode to overheat causing the blood surrounding the electrode to coagulate on the electrode. As the coagulum collects on the electrode, the impedance between the electrode and the site to which the RF wave is applied increases, thereby reducing the effectiveness of the electrode. As a result it is often necessary to stop the RFA in order to remove the coagulum from the electrode.
Accordingly, it is an object of this invention to provide an ablation catheter which is capable of generating both focal lesions and linear lesions while having the appropriate size, flexibility and maneuverability to enable it to be used effectively in a variety of RFA procedures.
Accordingly, it is also an object of this invention to provide for an ablation catheter with a linear electrode which is easily maneuverable and conforms readily to the arcuate shape of the interior of the heart while still having the appropriate size, flexibility and maneuverability to enable the ablation catheter to be used effectively in a variety of RFA procedures.
Accordingly, it is also a further object of this invention to provide an ablation catheter with a means for cooling the electrode in order to reduce the rate at which the coagulum builds up on the surface of an electrode while still having the appropriate size, flexibility and maneuverability to enable it to be used effectively in most RFA procedures.
Other objects and advantages of the invention will become apparent as the description proceeds.
To achieve these objectives, and in accordance with the purposes of the present invention the following ablation catheter is presented. As will be described in greater detail hereinafter, the present invention provides the aforementioned and employs a number of novel features that render it highly advantageous over the prior art.